Material cutting and testing machine



Aug. 19, 1941. STEWART 2,252,993

MATERIAL CUTTING AND TESTING MACHINE:

Filed Nov. 23, 1938 5 sheets-sheet 1 Zmnentor DON/7&0 EJEM/I/PZ 1 8 19, 1941- D. R. STEWART 2,252,993

MATERIAL CUTTING'AND TESTING MACHINE Filed Nov. 23, .1938

s Sheets-Sheet 2 3maentor Dan ma F. JI'EWA/PZ Aug. 19, 1941. D STEWART 2,252,993

MATERIAL CUTTING AND TESTING MACHINE Filed Nov. 23, 1938 5 She'ts-Sheet s Zhwentor Dam/7.40 fiJr-wqm Aug. 19, 1941, D. R. STEWART, 2,252,993

MATERIAL CUTTING AND TESTING MACHINE Filed NOV. 23, 1938 5 Sheets-Sheet 4 Bunentor flaw/r40 fi. J'TEWHRZZ Aug. 19, 1941. D, R, A T 2,252,993

MATERIAL CUTTING AND TESTING MACHINE Filed Nov. 25, 1938 5 Sheets-Sheet 5 33 Q: 3 5 I a;

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Zmventor Patented Aug. 19, 1941 MATERIAL CUTTING AND TESTING MACHINE Donald R. Stewart, Detroit, Mich.

Application November 23, 1938, Serial No. 242,038

12 Claims.

This invention relates generally to a machine forcutting material and testing the characteristics thereof and more particularly to a machine for testing the bond of abrasive articles.

It is an object of the present invention to proaway some of the material with a tool and to provide a machine of this character in which recording of the characteristics of the material will not materially vary with wear of the tool over a reasonable time period.

Another object of the invention is to provide a machine which will accurately record the characteristics of material by recording the energy necessary to operate a material removing or cutting tool over a predetermined operation of the tool.

Another object of the invention is to provide a machine for testing, among other characteristics, the machina bility of material by recording the electrical energy employed by an electrically operated tool and to provide a machine of this character in which the reading of the energy employed will not be affected by the usual fluctuations in line voltage.

Another object of the invention is to provide a new and novel machine for testing the bond of an abrasive article, such as a grinding wheel.

A further object of the invention is to provide a new and improved cutting tool and operating mechanism therefor.

Other objects of the invention will become apparent from the following description taken in connection with the accompanying drawings in which Figure 1 is a view in elevation of my machine;

Fig. 2 is a view of the machine taken substantially along the line and in thedirection of the arrows 22 of Fig. 1 and having parts rei moved and broken away to show certain details of construction;

Fig. 3 is a diagrammatical view of the electric circuit of the machine;

Fig. 4 is an enlarged fragmentary view of the machine showing in detail the mechanism which was removed from the view, Fig. 2;

Fig. 5 is a top plan view of part of the machine;

Fig.6 is an elevational view of the part of the machine shown in Fig. 5, and having parts broken away and in section;

Fig.7 is a view showing certain details of the machine and taken along the line 'I-'! of Fig. 6, and

Fig. 8 is a view in vertical section of the machine taken substantially along the line 8-8 of Fig. 1.

Referring to the drawings by characters of reference, the machine shown comprises in general, a driven tool ID, a driving power means ll,

control mechanism I 2, and an energy recorder I3, Fig. 3. In the present instance, the power means I l is an electric motor and the recorder, a standard rotating watt hour meter, is adapted to record the energy employed by the motor II in driving the tool for a predetermined operation controlled by the mechanism l2. Thus, with the tool I 0 acting on material irictionally such as, removing or cutting away some of the material, the load on the motor or electric energy employed thereby is recorded to give a corresponding indication of characteristics of the material, such as, its machinability, the character of the bond of an abrasive article, etc.

The machine includes a :base or standard l4 which is preferably provided with a horizontally extended or overhanging upper end portion l5 which may be hollow and formed in part by a top wall [6. The upper end ll) of the base is provided with extended, vertical guides I'l cooperable with guideways of a vertically, adjustably movable supporting member or plate I 8 which carries the tool I0, motor II, and the interconnecting mechanism therefor which is hereinafter describedin detail. The motor II is of the reversible type and may be rigidly secured to the vertically movable supporting plate I8 by bolts 20 or by any other suitable means. The motor II is adapted to drive or rotate a supporting structure for the tool ID, the supporting structure including a spindle or open ended tube 2| which is arranged to rotate about a substantially vertical axis and is journaled in vertically spaced bearing containers 22 which may be rigidly secured to the supporting plate I8 by screws and nuts 23 or by other suitable means.

The motor II is adapted to rotate the spindle 2| and to this end is provided with a depending drive shaft 24 having keyed or otherwise secured thereon, a drive gear 25 which meshes with and drives a gear 26 which is keyed, as at 21, to and adjacent the upper end of the spindle 2|, Fig. 8. A supporting member or casing 28 is provided with an upwardly directed tubular portion 29 which receives a lower end portion of the spindle 2|, the casing 28 being keyed, as .at 30, or otherwise secured to the spindle to rotate therewith. Within the spindle 2| is a rotatable shaft 3| which is coaxial with the spindle and secured to the lower end of the shaft 3| to rotate therewith,

a drive gear 32, within the casing 23, meshes with and rotates a bevel gear 33 which is internally threaded to receive an elongated worm gear or lead screw 34 having its axis of rotation transverse to the common axis of the shaft and spindle. Overlying the gear 33, the casing 28 is provided with an opening closable by a removable closure member or cover plate 35 which is preferably provided with an opening or bore 33 for rotatably receiving the worm gear 34 to give added bearing support thereto. Similarly, a

tubular insert or bearing member 31 is provided: in the casing wall 38, spaced from plate 35, to

receive and give further bearing support to the worm gear 34. Preferably, the lead screw 34 is provided longitudinally thereof with a keyway 34a and the cover plate 35 is provided with a key 35a cooperable with the keyway to prevent turning or rotating of the screw 34 so that rotation of gear 33 will cause the screw to move rectilinearly in the direction of its longitudinal axis. In the casing tubular portion 23, a thrust roller bearing unit has one race 48 thereof secured to a reduced extended portion or hub of the gear 33, the other race, as at 4|, having a convex bearing surface abutting a concave bearin surface of a ring-like abutment member 42 which is secured to the cover plate 35 in .an inner recess thereof.

The tool I!) is carried by a body or casing 44 which is attached to one end of the worm gear 34 for movement thereby transversely to the axis of the shaft 3|. To this end, the tool carrying body 44 may be provided with a bored recess to receive an enlarged cylindrical end portion or thrust bearing 45 provided on the end of a shaft together, The toolbody 44 is slidably supported L4 on the casting 41a which is provided with guideways' 55 to receive complementary guides on the body 44. r r

In order to provide a tool which will not wear quickly, I provide a hollow, frustro-conical tool, previously designated by the numeral l3, having an outer circular pushing or shearing or cutting edge 52. The term pushing edge is employed, since when the machine is employed to test the bond of an abrasive or grinding wheel the tool has a combination cutting and pushing action.

A freely rotatable shaft 53, is journaled in ball bearings 53a positioned in a relatively large openjing 54 in thebody 44 and these bearings may be spaced by a tubular spacer member 54a. The

shaft 53 is provided in the lower end thereof with a conical recess to receive the converging end portion of the tool is which may be rigidly secured to the shaft by a screw 55, preferably having a complementary tapered head to seat in the hollow frustro-conical tool. The axis of rotation of the cutter is arranged at an acute angle to the axis secured to the shaft by a set screw 6|, the spacer member seating on a bearing lock or retaining nut em. The spacer member 53 also provides a seat for a gear 33 having a bushing 52, the gear 63 being in mesh with and driven by a gear 64 secured on the drive shaft 24 of the electric motor II. On the upper end of the gear 63, clutch teeth are provided for clutching action with complementary teeth provided on the lower end of a vertically movable clutch member 65. The clutch member 65 is secured to the shaft 3| against rotation by a pin 33, the shaft having an elongated aperture 61 to receive the pin and perthe tool I!) being revolved bodily about the common vertical axis of the shaft 3| and spindle 2|.

The shaft 3| and the spindle 2| rotate in the same direction, but gears 33, 64 and gears 25, 23 are selected such that the spindle rotates faster than the shaft, and gears 32, 33 and 34 are selected whereby the tool revolves bodily at a greater rate than it is moved outwardly by the worm gear 34; As a result of the above mentioned speed differentials, the tool l3, offset from the axis of the spindle 2| is rotated by and upon rotation of the spindle and bodily travels or revolves spirally. A helical coil spring 66 surrounds the shaft 3|, under compression, and urges the clutch member 35 downwardly into coupling relation with the clutch teeth of the gear 63. The lower end of the spring 55 seats on the upper surface of the clutch member 65 and the upper end of the spring abuts a spring retainer 51 which is apertured to receive the shaft 3| and is limited in its upward movement relative thereto by lock nuts 33 scre'wthreaded onto the shaft. Preferably, the cooperating clutch teeth are angularly disposed, as shown, to provide for relative rotation or'slipping between theclutch parts. Slipping between the clutch parts occurs or may occur when on return of the tool ill to its starting position the tool body 44 engages the gear casing 28 as a stop. This clutch slipping action permits continued operation of the spindle without injury to the 7 machine.

reduction gears, designated in general by the numeral), the gears it being driven by a gear H mounted on and secured to the motor driven shaft 3|. Preferably, the speed reduction gears 13 are enclosed in a housing 12 having a removable top wall or cover 13 which may be rigidly secured in place by screws 14, or by other suitable means. Mounted on the cover 13, externally of the casing 12, the control mechanism preferably includes a rotatable control member which may be a disc, and this disc is secured to a vertical shaft 15 which is the driven speed reduced or take off shaft from the speed reduction gear train 10. Carried by and rigidly secured to the disc l5, a pair of radially spaced arms TI, 18 carry contact members 83, 8| respectively which may be adjustable relative to their respective supporting arms and to this end may be screws,

as shown. Mounted on the cover 13 externally thereof, a switch, designated in general by the numeral 82 is provided with a movable contact member 83 arranged to be engaged and actuated by the contact 80. Similarly, a switch 85 is provided with a movable contact or switch mechanism actuator 85 engageable and operable by the contact member 8|. Switches 82 and 85 are normally closed switches, which may be of any of the well known types and are therefore not shown nor described in detail.

Rigidly secured to the vertically movablesupporting plate I8 immediately below the housing I2,a support or bracket 81 is provided with a pairof spaced, upwardly directed side flanges 90 having aligned apertures or bores for receiving a pair of spaced, parallel supports or shafts 9|. The shafts 9| are arranged for endwise sliding or longitudinal movement in their supporting bores, transversely to the axis of rotation of shaft 3|, and these shafts carry the housing I2. Integral with and depending from the bottom wall of the housing I2, pairs of spaced bosses or lugs 92 are provided having aligning apertures to receive outer end portions of the shafts SI to which the bosses 92 may be secured by pins 94 or by other suitable means. The casing I2, speed reduction gears I and control mechanism I2 are urged as a unitary structure toward the drive shaft 3| by means, such as helical coil springs 95, only one of which is shown, for yieldably holding the gear train I0 in driving relation with motor driven gear II.

A shaft 97 is supported for rotation in aligning bores provided in a pair of spaced arms 98 which are integral with the bracket 81, and secured to the shaft 91, a cam I00 is arranged to engage a depending wall Id! of the housing I2 to move the housing to disengage the gear train I0 from the drive gear II. On or adjacent one end of the shaft 91, a lever I02 may be provided for rotating the shaft. A lever I03, pivoted intermediate its ends, as at I04 to the bracket 81 has one end I05 forked to engage in an annular recess I06 provided in the clutch member 65 and the other end I ll! of the lever I33 positions immediately beneath a cam I08 which is secured on and to the manually operable shaft 3! to pivot the lever to disengage the clutch. Carried by the lever end I31, an adjustable contact I09 is adapted to engage a movable contact or actuator H0 of a switch III which is disposed beneath the lever end I01 and is mounted on a bracket II2 which in turn is mounted on the vertically slidable plate I0. The switch III is a normally closed switch which may be of any suitable type.

The supporting plate I8 which carries the tool Ill, motor II, control mechanism I2, and the mechanism which operatively connects the tool and motor is provided with an integral lug or boss I I4 having a threaded aperture to receive a threaded screw H5 which is rotatably supported in a bore in the top wall of the hollow upper end I5 of the standard 44. Keyed or otherwise secured to the upper end of the screw II5, a gear H3 meshes with a gear II'I provided on a shaft which may be manually rotated by a hand wheel I I8. By means of the hand wheel H8, it will be seen that the entire mechanism carried by the vertically movable plate I8 may be raised or low.. ered with respect to the work or material as at I23 upon which the tool is to act. The tool is lowcred and forced into the material to a desired depth, and to ascertain the desired depth of penetration an indicator or dial plate H9 operated on rotation of the screw may be provided and retained by and under the head of the screw.

In order that a number of the herein described machines may give substantially the same reading for a given piece of material tested, I provide a brake I46 for each of the machines for frictionally engaging the spindles 2| and the friction applied by these brakes to their respective spindles may be adjusted by micrometer operated screws or by other suitable means. Thus, by adjusting the friction exerted by the brakes I46, a common frictional resistance to operation of the electric motors may be established whereby the test readings will be substantially identical for all of the machines for material under test having substantially like characteristics.

Referring now to the diagrammatical View of Fig. 3 which shows the electrical circuits of the machine, the watt hour meter, designated in general by the numeral I 3 may be of any suitable reversible induction motor II and similarly a side of the meter and the numeral I23 designating the voltage or potential side of the meter. Main lines which may be the usual 110 volt lines are designated by the numerals I24 and I25 and these main lead wires connect respectively to contacts 26 and I2'I of a reversing switch I28. The watt hour meter I3 is connected in the main line E25 and a lead wire I35 connects one terminal of the potential side or armature of the meter to the other main lead wire I24. In the lead wire I30 is a manually operable switch I3I provided to cutout the potential I23 of the meter to stop operation of the meter, and also in the line I30 is the manually operable, normally closed switch III which is adapted when switch I 3| is closed, to start the meter simultaneously with starting of the control mechanism I2. The reversible switch I28 includes the usual switch member designated I32 and two pair of contacts I33, I34. Lead wires I35, I35 connect the terminals I33 to the reversible induction motor I I and similarly a pair of lead wires I37, I38 connect the other pair of contacts I34 to the motor II. .The control switch 32 is diagrammatically represented as comprising a pair of spaced contacts I39 and its movable switch member 83 biased toward closed position to I101m2l1y bridge the contacts I39.

arms I8, 11 respectively which are mounted on the disc I5 which is rotated by the motor II through the speed reducing mechanism or gear train It. Contacts I39 are connected in the lead wire I38 in series with the motor II by lead wires I42, I43 and contacts I40 of the other switch are connected in the lead wire I35 in series with the motor II by lead wires I 44, I45. Control switch 85 is adapted to control operation of the motor rotating or driving in one direction or on cutting operation, and switch 82 is adapted to control operation of the motor II on reversing operation thereof or on return of the tool I0 to its starting position.

Operation The herein described machine operates as follows: Assuming that the material. I20 to be cut or testedis held securely in place below the tool I0, it is first desirable to make a circular starting out in the material to a desired depth below the outer crust thereof or to a depth where a more accurate or average hardness reading of the ma terial may be obtained. Assume further, that the tool. I is in its starting position, that is, with its body 44 adjacent to or abutting the gear casing 28 as a stop so that the tool will rotate through its minimum circular path. In order that the tool II) will travel a circular path on this first cut into the material, the clutch member 65 is disengaged from the driven gear 63, which disengagement renders inactive the lead screw 34 which is adapted otherwise for gradually increasing the radius arm of the tool as the tool rotates. Disengagement of the clutch is obtained by means of, the manually operable lever I02 which when pulled to the left and downward, Fig. 4 pivots the lever I03 in. a counterclockwise direction which raises the clutch member 05 out of engagement with the clutch teeth of the driven gear 63. Also upon pulling lever I 02 downward and to the left, facing Fig. 4, cam 'I 00 is rotated and engaging the casing wall IOI moves the casing to the left thereby disengaging the speed reduction gear train I0 from the drive gear I I, rendering the control mechanism ineffective for the first or circular cut. In addition, on pivoting the clutch operating lever I03, contact I09 carriedby the free end of the lever I03 depresses the control member III) of th normally closed switch III and' opens this switch. Thus, it will be seen that by pivoting the lever I02 counterclockwise, Fig. 4, the clutch member 65 is moved to unclutch gear 63 from the driven shaft 3|, gear train I0 is disengaged from driven gear II and switch III is opened. With the above mentioned drives in the positions stated and with control I! holding switch 82 open, Fig. 3, the motor II is started when the reversing switch I28 is in the position shown, providing of course that line switch I24 is closed. This circuit to the motor II is as follows: From line I24, contact I26, switch I28, contact I33, lead wire I44, bridged contacts I40, lead wire I45, lead wire I35, motor II, lead wire I36, reversing switch I32, contact I21 and back to the other main lead wire I25 through the field or amperage side I22 of the meter I3. Switches III and I3I are open cutting out the potential I33 of the meter I3 to prevent recording thereof since r ther is no point in recording the electrical energy employed during the initial cut into the material I20. With the tool rotating, it is lowered by the hand wheel to cut into the material a desired depth which is indicated on the dial plate spindle 2|. As the tool rotates it follows a spiral.

path and cuts or shears or pushes material gradually from the wall of the cut. Simultaneously with the spiral cutting action of the tool, the disc I5' is started to rotate in a clockwise direction,

through the speed reducing gear train I0. As the disc starts to rotate, contact 80 moves away from the switch control member 83 permitting the switch 82 to close and when the contact member 8| engages and moves the switch control member 86 of the switch 85, the switch 85 is opened breaking the circuit to the motor. During this operation, manual switch I3| is left open since this is only a preliminary cut and recording of the same by the meter I3 is not desired. The tool I0, ro-

' tating about and gradually moving out from the axis of the spindle 2| has now cut away a predetermined amount of material from the member I20, under control of the switch mechanism I2 and, leaving a flat substantially smooth surface at a predetermined depth below the outer surface of the material. By providing the initial cut to a suitable depth such that too much material is not removed and by selecting the proper speed ratio between the spindle and the lead screw such that .the tool will move out gradually, the initial spiral cut leaves a smooth finished surface, so that the final cut will remove a known or predetermined amount of material. After completion of the cut' the tool I0 is then returned to its starting position by operating the reversing switch I28 so that it engages contacts I34 which establishes a closed circuit to the motor I I through the now closed control switch 82. On reversing the motor and tool, the disc I5 will rotate in a counterclockwise direction facing Fig. 5 and when control contact engages the control member 83 of switch 82, the circuit to the motor is opened, stopping the tool I0. In the event of failure of the switch 82 to open the motor circuit on return of the tool I0 to its starting position, the tool carrying body 44 will strike the gear housing 28 and the gear 63 and clutch member 65 will slip by reason of the angularity of the cooperating clutch teeth thereby preventing injury to the machine.

With the tool I0 now returned to its starting position the final recorded cut is taken in the material I20. First the clutch member 65 by means of handle or lever I02 is again pulled down to unclutch gear 63 from shaft 3| so that to start the motor will only rotate the spindle 2| and the tool II] will rotate through a circular path of travel. Of course, as previously mentioned when the clutch member 65 is raised, gear train I0 is disengaged from motor driven gear II and switch III is opened. Manual switch I3I is now closed but it will be seen that the meter I3 will not register since switch I II is now open. The reversing switch is positioned to again engage contacts I33 and establish a circuit to the motor II through and controlled by the control switch 82. With the motor I I rotating the tool, the tool is forced down into the material by means of the hand wheel IIB to a predetermined depth indicated by the dial I I9. By releasing the lever I02, the clutch member I06 is instantly moved downward by the spring 66 into clutching engagement with the gear 63 and simultaneously spring moves gear train I0 into driving relation with drive gear II. Simultaneous with the above operations, switch II I closes the circuit of the meter potential I23. It will thus be seen that at the instant the tool I0 starts its spiral cutting action, control I2 is brought into action and meter I3 begins to record the energy employed by the motor ll to drive the tool. When the tool has completed its predetermined cut or travel, rotatable control contact I8 opens switch 85, stopping the motor. Since, the motor II will drive the tool I0 until the control arm travels from one contact to the other it will be seen that although control I2 is normally a time control, there will be no discrepancy in recording of the energy employed by the motor in the event of a voltage drop since this will only cause a slowing down of the motor with a corresponding slowing down of rotation'of the control since the control is driven by the motor. Thus, the meter I3 will record the electrical energy required to drive the tool and will correspondingly indicate the characteristics of the material, such as its machinability, or will indicate the character of the bond of anabrasive or grinding wheel. After the recording ismade the switch ,l3l maybe opened and the motor II is then reversed by changing the reversing switch I28 to the other pair of contacts and the tool H2 is returned to its starting position for the next piece of material to be tested. I

From the foregoing description it will now be seenthat I have provided a new and improved machine for testing certain characteristics of material, such as the machinability of metal and the character of the bond of an abrasive or grinding wheel. By providing a machine, the material removing tool of which operates to remove apredetermined amount of material over a predetermined area, a substantially accurate recordingof the characteristics of the material is obtained. Furthermore, by providing a machine of, the above mentioned character having a conical shaped cutting tool arranged to roll on a circular cutting edge and shear or crumble material, that the tool will not quickly become dull. Also since the machine is adapted to operate until a predetermined amount of material is removed or cut away from material under test, it will be seen that even though the tool in time be- I comes dull, the accuracy of recording of the machine will not be materially affected. In addition, it will be appreciated that by determining the characteristics of material by recording the electrical energy required to remove a predetermined amount of material from the piece under test that an accurate recording may be made and that such recording will not be affected by change in the voltage since the machine automatically stops when and only when the said predetermined amount of material has been removed. Another advantage of the present machine is that the work or material may remain fixed or stationary so that a minimum of power is required to opcrate the tool as compared to such machines in which both the material and tool move against each other which provides for a more accurate reading and entails a saving in cost of operation. Furthermore, I have provided a new and. improved machine for testing the characteristics of material by first removing material from a test piece down to a smooth surface and in so doing setting up strains and stresses in the material below said surface, then removing the stressed and strained material in the same manner that the first material is removed and recording the quantity of material removed the second time.

What I claim is: l

1. In a machine for testing characteristics of material, a cutting tool operable to cut the material, electrically operated means to actuate said tool, means to register the total electrical energy required to actuate said tool in making a predetermined out in the material, and control means actuated by said electrically operated means and operable to control the circuit of said registering means.

2. Ina machine for testing characteristics of material, a cutting tool operable to cut the material, electrically operated means to actuate said cutting tool, electrically operated means to register the electrical energy employed to actuate said tool and cut away a predetermined amount of material, control means operable to control the circuit of said registering means and actuated by said electrically operated means, and means operatively connecting said control means and said electrically operated means.

3. In a machine for testing characteristics of material, a cutting tooloperable to cut the maserial, electrically operated means to actuate said tool, means to register the total electrical energy required by said electrically operated means during the 'cutting operation, control means to limit the cutting operation, and clutch means operatively connectingsaid control means andsaid tool.

"4. In a machine for testing characteristics of material, a cutting tool operable to out the material, electrically operated means to actuate said tool, electrically operated means operable to register the electrical energy employed by said tool actuating means to out the material, means controlling the circuit of said registering means tolimit registering ofelectrical energy employed to a predetermined cutting operation of said tool, said controlling means being operable by said tool actuating means, and means to control operation of said controlling means by said tool by the tool operating means to indicate a corresponding hardness of the material under test, control means controlling said registering means and actuated by said tool actuating means, and means cooperating with said control means for controlling the electrically operated tool actuating means.

6. In a machine for tes ing characteristics of material, a tool operable to cut the material, means acting on said tool exerting a force to cut the material, means to indicate the application of said force exerting means, means controlling said indicating means, and means for stopping the tool after a predetermined operation thereof and controlling said first-named controlling means.

7. In a machine for testing characteristics of material, a tool operable to out the material, an electric motor to drive said tool, means for indicating the electrical energy used by said motor, control means for said indicating means and driven by said electric motor, said control means being bodily movable to a position disconnected from said motor, and means to move said control means.

8. In a machine for testing characteristics of material, a tool operable to out the material, an electric motor to drive said tool, means for indicating the electrical energy used by said motor,

control means for said indicating means and driven by said electric motor, said control means being bodily movable from one position in which it is driven by said motor to another position disconnected from said motor, means to move said control means from one to the other of said positions, and switch means operable upon bodily movement of said control means and controlling said indicating means.

9. In a machine of the character described, a driven tool, an electric motor driving said tool, a movable control member operable to control the circuit of and actuated by said motor, speed reduction mechanism operatively connecting said motor and said control member, said control member being movable between predetermined limits by said motor, and. means to indicate the total electrical. energy employed by said motor to drive said tool during movement of said control member between said limits.

ap'red'etermined amount of the material, and

switch means operable by said motor and automatically rendering said watt-hour meter inactive upon completion by said tool of the removal of said predetermined amount of material.

11. In a machine of the character described, a tool having an axis of rotation and also arranged to turn about another axis of rotation, means for increasing the radius arm of said tool as the tool rotates about said second-named axis, means operable to render said first-named means inefiective, an electric motor for turning said tool andfor driving said first-named means, control means for controlling said motor and driven thereby, speed change mechanism operatively connecting said control means and said motor,

said speed change mechanism being bodily movable to disengage said control means from said motor, an indicator for indicating the energy used by the motor and in circuit with said control means, and means for moving said speed change mechanism and also controlling said indicator and said first-named means.

12. In a machine for testing the bond of a grinding wheel, means for holding the wheel against movement, a spirally operable cutting tool for making a predetermined cut in the wheel, an electric motor for driving said tool, control means actuated by and controlling said motor and limiting operation of said tool'to a predetermined number of turns, means operatively connectin said control means and said motor, and electrically operated means for registering, the electrical energy required to oper-- ate said motor in turning said tool said predetermined number of turns and controlled by said control means.

DONALD R. STEWART. 

